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C. E. SCRIBNER. TESTING APPARATUS FOR MULTIPLE SWITGHBOARDS.

Patented Jan 4, 1898.

(N0 Mode 1.)

Mfimz'ses:

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBN ER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.

TESTING APPARATUS FOR MULTIPLE SWITCHBCARDS.

SPECIFICATION forming part of Letters Patent No. 596,629, dated January4, 1898.

' Application filed December 8, 1896. Serial No. 614,876. (No model.)

To all whom it may concern.-

Be it known that I, CHARLES E. SCRIBNER, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Testing Apparatus forMultiple Switchboards, (Case No. 436,) of which the following is a full,clear, concise, and exact description, reference being had to theaccompanying drawing, forming a part of this specification.

My invention concerns the test system which is commonly used in multipleswitchboards, particularly those which are employed in connection withsubsidiary line-signals controlled from the substations of thetelephonelines. It is a device for altering the electrical condition ofthe test-contacts of the line to make the line test busy T through theagency of the device controlling the subsidiary signal, so that the lineshall be caused .to test busy by the removal of the substation-telephonefrom its switch.

My invention is intended for use in connection with a particular systemof this type in which the subsidiary line-signal is in a local circuitcontrolled by a relay responsive to currents in the line and in which aseparate relay is provided in a local circuit which becomes closed whenconnection is made with the line and which serves more or less directlyto break the continuity of the circuit includingv the subsidiary signal.The circuits are so arranged in the systemin question thatthetest-contacts in the spring-jacks of the line become connected with asource ofcurrent through the agency of the plug used in makingconnection with the line. The present invention is designed to effect asimilar change in the electrical condition of the testrings through theagency of the relay or magnet controlling the line-signal.

The invention is shown in connection with such a system of signals inthe attached drawmg. sented connected by telephone lines withspring-jacks in different sections of a multiple switchboard and withsuitable signalcontrolling appliances. A single pair of operators plugsand their plug-circuit are shown in position to unitethe spring-jacks ofthe Therein two substations are repre-' two lines. The appliances at thesubstation are of the well-known type and arrangement for automaticallyoperating signals in the central office, the line-circuit normallycontaining a high resistance, but being closed through the telephonesduring the use of these instruments. The line conductors 1 and 2 leadfrom the apparatus of the station to spring-jacks a and a in differentsections of a multiple switchboard, and extensions from them lead toearth and through a relay 1) and battery 0 to earth, respectively. Thespringjacks are provided with the usual test-contacts in the form ofrings (1 in' front of the linecontacts and accessible for testing. Theserings are united by a grounded conductor 3, in which is included arelay-magnete, controlling two pairs of switch-contacts, which areinterposed in the line conductors 1 and 2, respectively, and serve tobreak the earth connections of these conductors when the relay 6 becomesexcited. The relay 7) controls through its armature a pair ofswitch-contacts included in a local circuit 4 5, containing a source ofcurrent f and a subsidiary signal g, which may be a small incandescentlamp. Thislamp, which constitutes the line-signal, maybe associated withone of the spring-jacks of the line in one section of the switchboard.

The conductor 5 of the local circuit is connected with the test-ringsthrough a resistance-coil m. This coil may have a resistance of onehundred ohms and may for convenience be wound non-inductively on thespool of the cut-off relay 6.

The usual plugs h and 71, are furnished the operator for unitingspring-jacks of diiferent lines. The like line-contacts of the plugs areunited by conductors 6 and 7, which constitute the plug-circuit. Theswitch contacts of the usual calling-key i are interposed in theseconductors for connecting a source of signaling-current (not shown) withthe calling-plug h. A listening-key 7c is also furnished for connectingthe operators telephone Zin a bridge of the plug-circuit. Apermanently-closed bridge of the circuit 6 7 is formed by a conductor 8,which includes the source of current 0, together with the windings oftwo impedance-coils. The winding n of one of these impedance-coils islocated in the conductor 8, between the battery and conductor 7 of theplug-circuit, and the two windings n and n of the other are interposedbetween the other pole of the battery and conductor 6 of theplug-circuit, being normally connected in multiple at their outerextremities through the agency of contact-points 70 k of thelistening-key, which are closed together when the key is in position todisconnect the telephone from the plug.- circuit. The peculiararrangement of helices n and n together with the ground connection ofconductor 8, is for the purpose of isolating the tip of plug h duringthe act of testing in order that false test-signals may not be producedby changing electrical conditions in the remainder of the plug-circuitwith which it is associated.

The plugs h and h are provided with sleeveswhich register with the rings61 of the springjacks into which they are inserted. These sleevesconstitute the terminals of conductors 9 and 10, leading tothe free poleof the grounded battery f. Interposed in these respective conductors aresupervisory signallamps p andp, each of which is associated with one ofthe plugs h and h. The current through these supervisory signals iscontrolled by relays q and q, whose magnets are interposed in theconductor 7 of the plugcircuit on opposite sides of the connectiontherewith of battery 0 and which act when excited to close shunts aboutthe supervisory signals.

In the operation of this switching system the removal of thereceiving-telephone from its switch at a station permits the creation ofa current in the circuit by the central battery 0, whereby the relay 1)is excited and the local circuit 4 5,including the subsidiary linesignalg, is closed. This operation causes the lighting of the subsidiaryline-signal, and at the same time connects battery f with the test-ringsd of the line, thereby changing their electrical condition. In responseto the display of the line-signal the operator inserts plug h into theanswering jack a, at the same time bringing her telephone intoconnection with the plug-circuit 6 7 by means of key 70. She is then inposition to communicate with the calling subscriber and to learn hisorder for the required connection. It will be observed that theinsertion of the plug into the spring-jack has caused the excitement ofcut-oft relay 6 through the agency of circuit 9 3, and hence hasefiected the severing of line conductors 1 and 2 from their normal earthconnections, and has thus brought about the opening of circuit 4 5 andthe extinction of line-signal g. The

test-rings' of the line remain still electrifiedto a difference ofpotential from earth on account of their connection through wire 9 withbattery f, although their other connection with the battery has beenbroken. The operator makes the test of the required correspondent linein the usual way by applying the tip of plug it to a test-ring d of theline. Obviously if these test-rings are in their normal condition noelectrical change in the condition of the test-plug will be effected.If, however, battery f be connected with them through the action of theline-relay b or through the action of a plug inserted in the spring-jackof the line to make a connection upon a distant section of theswitchboard, current will flow from the test-ring to the tip of the plugand thence through the portion of conductor 6 including winding of toearth. This current will create a corresponding induced current in thehelix n which will find circuit through the operators telephone and willproduce a characteristic testsignal therein. Having tested the line andfound it free for use, the operator inserts the plug it fully into thespring-jack and operates the signal bell at the substation by means ofalternating current applied through the calling-key When upon theinsertion of plug h into the spring-jack a of the callin g-line currentwas permitted to flow in conductor 9, including the supervisory signal19, this signal was not lighted, because current was simultaneouslycreated through the relay q, whereby the current was diverted from thesupervisory lamp. In the instance of the insertion of plug it into thespring-jack of the line called for current is similarly set up inconductor 10, terminating in that plug, whereby the cut-off relaye ofthe correspondent line is caused to break the ground connections of thatline; but since the line-circuit is as yet incomplete at the substationthe relay q remains inert and the shunt about the supervisory lamp p isopen. Hence this lamp becomes lighted by the current through it andremains in that condition until the circuit at the substation becomesclosed in the removal of the telephone there from its switchhook foruse. If either of the connected subscribers should replace his telephoneupon its switch, the corresponding supervisory lamp p or 19 will becomelighted. When both signals have thus become lighted, their simultaneousdisplay may be taken as indicating a discontinuance of conversation, andthe plugs may be removed and returned to their normal conditions.

I claim as new and desire to secure by Letters Patent 1. The combinationwith a telephone-line, spring-jacks therefor in different sections of amultiple switchboard and test-contacts in the spring jacks, of a relayresponsive to currents in the line and a signal controlled thereby, acut-cit relay adapted to interrupt the current through the saidsignal-controlling relay when excited, and means for applying current tothe cut-01f relay in the act of making connection with the spring-jack,a source of electric current, and a circuit therefrom to the test-ringsclosed by switchcontacts actuated by the said signal-controlling relay;whereby the circuit connecting the battery with the test-rings is closedwhen the signal-controlling relay becomes excited, and is broken whenconnection is made with the line, as described.

2. The combination with a telephone-line, spring-jacks thereof indifferent sections of a multiple switchboard, and test-contacts in thespringjacks, of a relay responsive to currents in the telephone-lineduring the use of the line, a local circuit including a source ofcurrent together with a subsidiary signal controlled by the relay in theline, the relay being adapted to bring the source of current intoconnection with the test-rings when the said circuit is closed, acut-ofi relay adapted to interrupt the current through the line-relaywhen excited in a circuit terminating in the test-contacts, a conductorforming the terminal of a source of current adapted to be applied to thetest-rings through a plug inserted in one of them, and means for testingthe electrical conditionof the said contacts, substantially asdescribed.

3. The combination with a telephone-line and means for producing currenttherein while the telephone is in use, spring-jacks for the line indifferent sections of a multiple switchboard, and test-contacts in thespringjacks, of a relay responsive to currents in the line, oneswitch-contact of the relay being connected to earth through a source ofcurrent, and the other being connected with the test-rings through aresistance-coil and CHARLES E. SORIBNER. I

Witnesses:

ELLA EDLER, DUNCAN E. WILLETT.

